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Experts warn against sea dyke proposal

Update: March, 19/2012 - 10:26

by Phuoc Buu

 

A plan for a proposed dyke that aims to prevent flooding in HCM City has met with strong opposition. — File Photo

HCM CITY — A number of leading academic experts have voiced strong opposition to a flood-prevention proposal that calls for construction of a sea dyke connecting the coastal regions of Ba Ria-Vung Tau and Tien Giang provinces.

The tentatively named Go Cong-Vung Tau sea dyke, an idea initiated by Deputy Minister of Agriculture and Rural Development Prof Dao Xuan Hoc, has met with opposition for more than a year because of its environmental and economic impact.

Its main purpose, to prevent flooding in HCM City, cannot be realised, according to experts.

The dyke would have a length of 23km and extend from one point on the coastline near Vung Tau City to another point on the coastline off Go Cong District in the Cuu Long (Mekong) Delta province of Tien Giang.

The dyke would block the strait, which was created by two land cliffs in Vung Tau City and Go Cong District, thus turning the area into a 56,000ha lagoon, with a total volume of 3.3 billion cu.m of water.

The dyke, which would cost about VND50 trillion (US$2.4 billion), would also block the Soai Rap, Long Tau and Thi Vai estuaries, the three key gateways for vessel circulation to HCM City and Dong Nai and Ba Ria-Vung Tau provinces.

The dyke would have an entrance that would close and open for vessels and a 500m sluice for water flow.

Prof Le Huy Ba of the Institute of Science, Technology and Environment Management has opposed the proposal, saying the dyke would have only "tiny economic benefits in agriculture and aquaculture, and would create severe losses to the economy and environment".

Many experts agree with Ba, saying the dyke would create serious irreversible environmental problems.

Prof Nguyen Ngoc Tran, former member of the National Assemblys Foreign Affairs Committee, said the dyke would change the hydrographic conditions of both the areas outside and inside the dyke.

The coastal section where the dyke would not cover, in Go Cong and the coastal area of Ben Tre Province, would become heavily eroded, he said.

When the dyke blocks tides, the areas around Can Gio Mangrove Forest, which has semi-diurnal tides and a natural cleaning mechanism, would change completely.

Ba and Tran said these changes would kill the forest. Tran added that alluvia soil from the rivers of Vam Co, Soai Rap and Dong Nai would create large deposit mounds in the areas, causing a lower water capacity for the lagoon.

Experts are also concerned that the lagoon would become an unexpected huge reservoir of waste water.

"The dyke blocks the escape route to the sea for waste water from HCM City and the provinces of Dong Nai, Binh Duong and Long An," Tran said. The four cities and provinces are the biggest industrial hubs in the south.

Associate Prof Hoang Xuan Nhuan of the Port, Waterway and Continental Shelf Association warned about economic damage as well.

"The dyke would spoil the planning of the seaport systems for the southern key economic zone by blocking the Soai Rap and Thi Vai rivers," he said.

Experts argue that vessels coming to a wide range of ports in HCM City and Ba Ria-Vung Tau would face many inconveniences because of the dyke. Although there would be an entrance for vessels, it would be open only part of the time.

Nhuan added that the dyke would degrade the channels for vessels, and the dredging of canals would be prohibitively expensive.

"Construction and operation of the vessel entrance, which is under sea water, would cost a lot," he said.

Nguyen Van Tang of Song Cau Watery Work Consultation and Construction Company agreed about the high construction and operation costs. He said the dyke would be essentially "worthless".

"The dyke would work in the dry season, but not in the rainy season," he said. "Theoretically, the lagoon created by the dyke would work well only if the water in the lagoon is at its lowest level. When heavy rains occur and water from upper reservoirs near HCM City flow down to the lagoon, the sluice gate will have to open so the water in it can be discharged into the sea, thus lowering the lagoons water level."

"But what if the tide is high at the time that the sluice needs to open to release water?" he said, adding that water from the Sai Gon and Dong Nai rivers and heavy rains, as well as high tides entering from the south, would cause the lagoon to be too full.

Many leading professors in the field said it was crucial to prevent flooding in HCM City, but they have urged the Government not to build such a dyke, saying it would create economic and environmental problems.

Prof Nguyen Tat Dac of the HCM City University of Industry has developed another proposal that would block only part of the Soai Rap estuary. This proposal is one of several options being considered for flood prevention in HCM City.

Speaking to Viet Nam News yesterday, Director of the agriculture ministrys Dyke Management and Flood and Storm Control Department Nguyen Xuan Dieu said the proposal had just been put forward for consideration.

If approved, it would take 20-30 years for the proposal to be operational, as directed by the Government, he added. — VNS

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